RBG-31206, NPDES Noncompliance Notification:On 890628,bypass & Limitation Violations Found.Caused by Storms.Bypass of Filter Initiated,Establishing Flow of About 37 Gpm Through Three Available Package Plants

NPDES Noncompliance Notification:On 890628,bypass & Limitation Violations Found.Caused by Storms.Bypass of Filter Initiated,Establishing Flow of About 37 Gpm Through Three Available Package Plants

ML20246F437
Person / Time
Site:	River Bend
Issue date:	07/03/1989
From:	Odell W GULF STATES UTILITIES CO.
To:	Knudson M TEXAS, STATE OF
References
RBG-31206, NUDOCS 8907130252
Download: ML20246F437 (4)

Text

_ _ _ _ _ _

)

j GULF STATES UTILITIES COMPANY RNER BENO $7ATION POST 08Fici BOX 220 ST FRANC $vlLLE LOUT $1ANA 70775 AllE A CODE $04 635 6094 346 8651 July 3, 1989 RBG-31206 File Nos. G1.11.7 Mr. Myron Knudson, P. E.

Director, Water Management Division (6W)

U. S. Environmental Protection Agency Allied Bank Tower at Fountain Place 1445 Ross Avenue Dallas, TX 75202-2733

Dear Mr. Knudson:

NPOES Permit No. LA0042731 River Bend Station - Unit 1 This letter is a follow-up to a telephone notification initiated at 4:05 p.m.

on June 28, 1989, concerning unanticipated bypasses and associated effluent limitation violations at sanitary wastewater treatment system outfalls regulated by NPDES Permit No. LA0042731.

Outfall 004 is " treated sanitary waste from power station," an effluent which normally is processed by one or a combination of up to four extended aeration package treatment plants followed by sand filtration. The total combined "apacity of the package plants is 72,000 gallons per day (gpd), which was necessary at the height of construction in the mid-1980s. However, under the normal operating conditions of recent years flows have averaged less than 30,000 gpd with the bulk occurring during normal working hours of weekdays.

One of the larger (25,000 gpd capacity) package plants has been isolated for aerobic digestion of sludge so that the existing (readily-available) system capacity is 47,000 gpd. By adjustment of weir plates in the equalization basin, the throughput is normally cut down to about 20,000 gpd for nights and then increased gradually as needed through the days. ,

Storms associated with Tropical Depression Allison generated almost five inches of rain at River Bend Station between 5:00 and 9:00 a.m. on June 28, 1989. With soils saturated and local streams already high from rains of preceding days, the morning deluge of the 28th caused brief but extreme flooding of areas which ordinarily drain well. When the operator arrived at the sewage treatment facility at about 6:00 a.m. he noticed abnormally high flows and, suspecting stormwater intrusion, made adjustments to establish maximum throughput capacity of 47,000 gpd. It soon was evident, however, that the hydraulic surge was disrupting the sludge blanket in one package plant, threatening carry-over that would disable the sand filter. He then contacted environmental personnel to inform them of the need to bypass the filter. At 8:30 a.m. bypass of the filter was initiated, establishing a flow of about 37 gallons per minute (gpm) through the three available package 8907230252 890703 T gDR ADOCK 05000458 PNU ,

s p Knudson Page 2 plants. This was sufficiently greater than the total available capacity (about 33 gpm) to cause " lifting" of the sludge in one package plant to persist. In consultation with environmental personnel it was decided that diversion of a small amount of the high-diluted influent (" raw" sewage) was l

preferable to allowing extensive sludge carry-over.

Thus, at about 9:00 a.m. flows from the equalization basin to the package plants were cut back slightly, causing an estimated 4gpm of wastewater to bypass treatment completely. The latter continued at a gradually decreasing rate until 11:00 a.m.; thus we estimate that a worst-case total volume could have been as much as 1,000 gallons. The bypass of partially treated wastewater around the sand filter was secured at noon, with the resulting total flow over 3.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> measured at 7,833 gallons.

I Grab samples of the respective bypass effluents were collected at 9:25 a.m.

The partially treated water met total residual chlorine (TRC) and pH limits, but contained 312 mg/l of total suspended solids (TSS) in violation of the maximum limitation of 45 mg/1. The completely untreated effluent met pH limits, but contained no TRC in violation of the required minimum of 0.8 mg/l and had a TSS concentration of 235 mg/1. Results of analyses for biochemical oxygen demand (BOD ) are as yet unavailable; they will be provided in a subsequent letter ifS in violation of the 45 mg/l maximum limit or only included in the monthly Discharge Monitoring Report (DMR) if in compliance.

We do not expect that the BOD levels will be much, if any, higher than the maximum limitbecausemostoftheexcesssolidscontributingtothehighTSS levels appeared to be soil entrained by rain.

The stormwater intrusion was apparently due primarily to inundation of the open orifices of two sanitary sewer lines which had been disconnected from construction facilities. Some, of course, impinged directly as almost 5 inches of rain on the open equalization tank and package plants. The two abandoned sewer line orifices are situated in areas which normally do not flood even in high rainfall , or, if so, the duration of inundation is relatively brief. Both openings were obscured by structures and/or dense vegetation. Once the emergency adjustments had been made as described above at the treatment facility, personnel began searching for the source (s) of intrusion. One of the orifir.es was found fairly rapidly and plugged and the second was found a few hours hter and plugged. When the second opening was closed all obvious stormwater Lecsed entering the lift station involved.

To prevent recurrence of such problems we plan to permanently plug the two lines mentioned above and to verify by field investigation that they were indeed the only sources of intrusion.

Outfall 005 is " treated sanitary waste from training center to Grants Bayou,"

an effluent which normally is processed by a 15,000 gpd capacity extended aeration package treatment plant followed by passage through a 0.25-acre facilitative/ anaerobic polishing pond The pond is on a terrace overhanging the West Fork of Grants Bayou, and at the case of a steep slope from adjacent higher terrain. Diversion ditches normally shunt runoff from the slope around the pond, but are not adequate to handle extreme stonn events.

=

Knudson Page 3

~

By direct impingement on the pond surface and intrusion from the flooded diversion ditches, the storm event described above caused an estimated 100 gpm -of overflow frotn the pond to begin at about 8:00 a.m. This bypass continued at a gradually decreasing rate until about 1:00 p.m., allowing a worst-case total volume of up to 30,0.00 gallons of partially treated effluent to enter Grants Bayou.

Grab samples of treated and partially treated (bypassed) pond effluent were collected at 11:25 a.m. on June 28, 1989. The treated pond effluent met TSS, TRC, and pH limits. Overflow from the pond met TSS and pH limits, but contained no TRC in violation of the minimum limit of 0.8 mg/1. As in the case of the Outfall 004 bypass, results of the as yet incomplete BOD analyses for Outfall 005 will be provided in a subsequent letter if ib violation or only included in the June DMR if in compliance.

To prevent recurrence of overflows at Outfall 005 we plan in the near-term to upgrade the capacity of the diversion ditches as much as practicable. The entire treatment system at Outfall 005 was the subject of a recent evaluation by consulting engineers. Results and recommendations of this study are being assessed by upper management to determine the best long-term solution.

I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who ranage the system, or those persons directly responsible for gathering the information submitted, the information submitted is, to the best of my knowledge and belief, true, accurate and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations.

Sincerely.

. Ode 1 Manager-Administration WH0/LAE/RJK/ICfJVC/ch cc: Ms. Maureen O'Neill, Assistant Secretary Office of Water Resources Department of Environmental Quality P.O. Box 44091, Capitol Station Baton Rouge, LA 70804-4091

j ti-. l

.y:

'U-1' U.: 5.'. Nuclear Regulatory Comission ;j Document Control Desk-

. , . , -: - l Washington, D.C. 20555 l.. 4 L U.= S. Nuclear. Regulatory Comission 611 Ryan Plaza Drive, Suite 1000 Arlington,;TX 76011 NRC Resident Inspector =

Post Office Box 1051' St. Francisville, LA 70775.

l-llq l'

l' 1<

l'

- _ . _ _ - _ _ - _ _ . . - - - _ .